B. Sbarufatti (INAF-IASFPA), P. Romano, C. Guidorzi (Univ. Bicocca &
A. Moretti (INAF-OAB) report, on behalf of the Swift-XRT team
We have analysed the first three orbits of Swift XRT data for GRB070621
(Sbarufatti et al., GCN Circ. 6560), consisting of 150 s in Window
mode data and 1.3 ks in Photon Counting mode.
The UVOT enhanced XRT position (Sbarufatti et al., GCN Circ. 6567) is
RA, Dec = 323.79225, -24.81752 which is equivalent to:
RA (J2000): 21 35 10.14
Dec (J2000): -24 49 03.1
with an uncertainty of 2.0 arcsec (90% confidence).
The X-ray light curve exhibits an initial steep decay (index -3.8
up to T+380 s. A flare is observed around T+150s. After the break, the
count-rate decays with a power-law index of -0.91 +/- 0.04. If the
slow decay continues, the predicted count rate 24h after the trigger is
2.1E-2 counts/s, corresponding to a flux of 1.8E-12 ergs cm^-2 s^-1.
The WT and PC spectra can be fitted simultaneously with an absorbed
power-law model with a photon index 2.5+/-0.3 and a column density
(4.4 +/- 0.9)E21 cm^-2, significantly in excess with respect to the
galactic value (3.5E20 cm^-2, Dickey & Lockman, 1990). The absorbed
(unabsorbed) fluxes are 8.4E-10 (2.2E-09) ergs cm^-2 s^-1 for
the WT spectrum and 1.4E-11 (3.6E-11) ergs cm^-2 s^-1 for
the PC spectrum.
This circular is an official product of the XRT team.